Retargeting of viruses or VLPs

A polyomavirus or polyomavirus-derived virus-like particle (VLP), wherein the virus or VLP carries on its surface at least one targeting molecule that binds to a cell of interest, and wherein the at least one targeting molecule has been bound to the surface of the virus or VLP via:

• (i) a glycosylation of the at least one targeting molecule with at least one glycosyl residue, wherein said at least one glycosyl residue is recognised and bound by the polyomavirus or polyomavirus-derived VLP, and wherein the at least one glycosyl residue comprises α2,3-, α2,8-, or α2,6-SA;
• or
• (ii) the interaction between at least two interaction molecules, wherein a first interaction molecule is glycosylated with at least one glycosyl residue, wherein said at least one glycosyl residue is recognised and bound by the polyomavirus or polyomavirus-derived VLP;
• and wherein the at least one targeting molecule is conjugated to a second interaction molecule capable of interacting with the first interaction molecule, and
• wherein the at least one glycosyl residue comprises α2,-3, α2,8-, or α2,6-SA.